In Tempestate Securitas?

It's a religious medal to be sure.

Obverse is Saint George slaying the dragon

Reverse refers to the bible story in Matthew 8:23-27, Mark 4:35-41, and Luke 8:22-25 in which Jesus and his disciples were crossing the Sea of Galilee when a storm struck the boat. Jesus was taking a nap, and had to be woken by his disciples - he reprimanded them for their lack of faith, and calmed the storm instantly.

I can find a lot of similar medals online, but not a match. Based on the engraver's signature, I would guess late 19th or early 20th century?

This is commonly known as the Seaman's medal, although yours varies from the norm quite a lot.
Obverse:
St. George, mounted, slaying dragon
Around which you would usually find:
St. GEORGIUS EQUITUM PATRONUS
(St. George Patron Saint of Knights)
Reverse:
The story of Christ calming the waters.
Mark IV, 37-41
A storm tossed ship containing a sleeping Christ
and two frightened Apostles
Around which:
INTEMPESTATE SECURITAS
(Safety in the storm)
You can read all sorts of nonsense about these on ebay. Here's the true story:
The obverse comes from a coin called a Mansfeld thaler. First minted in 1521, it was commissioned by a
Count vonMansfeld and honoured his family's patron saint. The von Mansfeld family trade was warfare and his symbol was adopted for luck by his mercenary troops.
Skipping forward a century or so and the thaler had been replaced by a charm or amulet bearing St George but now with the addition of Christ on the reverse.
This design is generally credited to a Hungarian engraver, Christian Hermann Roth and, with modifications, has been in continuous production ever since.

Yours is the first that I've seen without the St Georgius and most certainly the first signed piece. Sadly I can't make out the signature.
The weight and diameter would also be interesting.

Could be the French sculptor Raymond Tschudin. Not his usual signature, but the letters seem to match pretty well.